Multiple errors in console using react@15.5.4; React.createClass deprecated; Accesing PropTypes

[jeremyjones313]

Warning: ElementalAlert: React.createClass is deprecated and will be removed in version 16.

Accessing PropTypes via the main React package is deprecated.

I would like to know your plans to upgrade your code to address these issues. I am very interested in using your components but am concerned they will prohibit me from keeping React up to date.

If you are already planning to address these issues could you provide a target date for availability on npm?

Thank you.

[jossmac]

Related to #200

@jeremyjones313 Would love a PR for this